Primer composition

ABSTRACT

A primer composition for use in the bonding of asphalts comprising the reaction product of an elastomer and a terpene resin. The primer composition of this invention can be used in the treatment of substrates to which asphalts are bonded to improve the bonding relationship between the substrate and the asphalt, such as in road-paving applications, roofing applications and the like.

This invention relates to primer compositions, and more specifically toprimer compositions for use in improving the bonding relationshipbetween asphalts and substrates to which the asphalts are bonded.

In copending application Ser. No. 167,986, filed July 14, 1980 nowabandoned, the disclosure of which is incorporated herein by reference,there is disclosed a chemically-modified asphalt composition which issuitable for use as an adhesive. The adhesive composition described inthe foregoing application is prepared by reacting an asphalt with apolymerizable vinyl aromatic monomer such as styrene and a depolymerizedrubber, either alone or in combination with a rubbery polymer, andoptionally a terpene resin. The resulting composition has been found tobe highly suitable in bonding a rubberized asphalt composite reinforcedwith glass fibers to a substrate in, for example, road-paving, roadrepair and roofing applications.

It has now been found that the adhesion between the composites coatedwith the chemically-modified asphalt as described in the foregoingapplication and a substrate can be significantly increased where thesubstrate is treated with a primer composition which is compatible withthe asphalt and with the substrate.

It is accordingly an object of the present invention to provide a primercomposition for use in improving the bonding relationship betweenasphalt adhesives and substrates to which they are bonded.

It is a more specific object of the present invention to provide aprimer composition for use in the coating of substrates to deposit onthe substrate a modified rubber composition to improve the bondingrelationship between the asphalt and the substrate.

The concepts of the present invention reside in a primer composition foruse in improving the bonding of asphalt to substrates wherein the primercomposition is prepared by reacting an elastomer with a terpene resin.It has been found that the primer composition of this invention, whenapplied to a substrate to which a chemically-modified asphalt is to bebonded, serves to increase the adhesion between the chemically-modifiedasphalt and the substrate and to decrease the temperature at whichadhesion between the substrate and the asphalt composite can beeffected.

In the practice of the present invention, an elastomer is reacted with aterpene resin, and the resulting composition is then dispersed in asuitable solvent, thus permitting the reaction product to be applied asa coating on the surface of the substrate to which the rubberizedasphalt composite is to be bonded. The elastomer employed as one of thereactants in the present invention is preferably a depolymerized rubber.The term "depolymerized rubber", as used herein, is intended to includeand refer to a number of commercially available, low molecular weightnatural and synthetic polymers. Depolymerized rubbers are generallyrubbers which have been depolymerized to reduce their molecular weightby treatment with a depolymerizing agent, such as alkali; the rubberswhich can be depolymerized include not only natural rubber but alsosynthetic rubbers, such as depolymerized synthetic conjugated dienepolymers (e.g., depolymerized synthetic polyisoprene, depolymerizedsynthetic polybutadiene and depolymerized synthetic polychloroprene).Generally, depolymerized rubbers employed in the practice of thisinvention have average molecular weights ranging from 10,000 to 110,000.Various depolymerized rubbers are available commercially, includingdepolymerized rubbers available from Hardman Chemicals under thetrademarks "Isolene", which are comprised of a series of depolymerizedvirgin synthetic polyisoprene polymers and the various "DPR" rubberswhich are depolymerized natural rubbers. In general, such depolymerizedrubbers are in the liquid state at ambient temperatures, and are quitetacky.

The depolymerized rubbers as described above are reacted with a terpeneresin which can be any one of a number of synthetic polyterpene resinscommercially available. Suitable resins include the polyterpene resinsmarketed by Goodyear Chemicals under the trademark "Wingtack", includingthe Wingtack 95 resin, a synthetic polyterpene derived from C₅hydrocarbon resins. Another Wingtack resin useful in the practice ofthis invention is Wingtack 115, a resin chemically similar to Wingtack95, except that Wingtack 115 has been polymerized to a higher softeningpoint. Another series of terpene resins suitable for use in the practiceof this invention are the terpene resins manufactured by the HerculesIncorporated under the trademark "Piccolyte", including the A100, A115,A125 and A135 resins. These are derived from the monomer alpha-pinene.Yet another series of terpene resins which can be used in the practiceof this invention are the terpene resins marketed by Neville ChemicalCompany under the trademark "Nevpene", such as Nevpene 9500.

The reaction is carried out by simply blending the rubber and thepolyterpene resin at a temperature sufficient to enable the reactionbetween the two to take place. In general, use can be made of reactiontemperatures ranging from 50°-300° F., with higher temperatures beingpossible to provide reduced reaction times.

The relative proportions between the rubber and the terpene resin can bevaried within wide ranges, and generally are not critical to thepractice of the invention. In general, best results are usually obtainedwhen the composition is formulated of 5-40% by weight of the rubber and95-60% by weight of the polyterpene resin. If desired, suitable solventsfor the reactants can be employed in carrying out the invention. Ingeneral, when use is made of a solvent for each of the two reactants,the solvent is a hydrocarbon, hexane being frequently preferred.

It is also possible, and sometimes desirable, to include in the reactionmixture, a non-depolymerized elastomer. As the non-depolymerized rubberor elastomer, use can be made of a number of elastomeric materials wellknown to those skilled in the art. Included are both natural rubbers andsynthetic rubbers. Suitable synthetic rubbers are homopolymers ofconjugated dienes (i.e., butadiene, isoprene, chloroprene, etc.) as wellas elastomeric materials formed by copolymerization of one or more ofthe foregoing conjugated dienes with one or more ethylenic monomers suchas styrene, acrylonitrile, methacrylonitrile, acrylic acid, methacrylicacid, etc. Included in the latter category are butadiene-styrenerubbers, butadiene-acrylonitrile rubbers andacrylonitrile-butadiene-styrene rubbers. Particularly well suited foruse in the practice of this invention when a non-depolymerized rubber isemployed is the butadiene-styrene rubber marketed by Philips Petroleumunder the trademark "Solprene 1205C".

The amount of the non-depolymerized elastomer is similarly not criticalto the practice of the invention, and can be varied within relativelywide ranges. In general, good results are obtained when thenon-depolymerized rubber varies from 1 to 30% by weight of thecomposition based on the total weight of the composition.

As is indicated above, the primer composition of this invention isparticularly useful as a primer to secure a bonding relationship betweena glass fiber-asphalt composite of the sort described in the foregoingcopending application Ser. No. 167,986 now abandoned. As described inthat application, the composite is formed of a bundle of glass fiberswhich has been coated, or impregnated, with a non-tacky rubber-modifiedasphalt composition of the type described in copending application Ser.No. 045,047, filed June 4, 1979. In general, the bundle of glass fibersserving as reinforcement for the non-tacky rubber-modified asphalt arepreferably present in the form of a woven roving such that the compositehas the configuration of a road repair laminant, mat or membrane to belaid down over a substrate whereby the mat is then overlaid with, forexample, a wear surface of, for example, asphalt. To insure adhesionbetween the composite and the substrate there is an adhesive coating onone surface of the mat, with the adhesive coating being formed of thereaction product of asphalt, a polymerizable vinyl aromatic monomer anddepolylmerized rubber as described in copending application Ser. No.167,986 (now abandoned). As described in that copending application, thereaction product may also be blended with a terpene resin to enhance thetackiness of the coating as an adhesive.

The primer composition of this invention is simply applied as a thincoating on the substrate, whether it be a concrete, asphalt or bricksubstrate. The primer composition of this invention thus serves to coatthe substrate and is compatible with the adhesive coating on drying toinsure that the mat having the adhesive coating on one face thereof issecurely bonded to the substrate.

For that purpose, the substrate should be coated with a quantity of theprimer composition of this invention to establish a secure bondingrelationship between the substrate and the adhesive coating on the mat.In general, the coating has a minimum thickness of 1 mil, and can rangeup to an inch or more, although thick coatings of the primer compositionof the invention generally afford no greater advantage.

Preferably the primer compositions of the present invention are appliedunto a substrate as a solvent solution suitably containing about 5-15%by weight of solids. Outstanding results are obtained using 10-12%solids. Numerous solvents including aromatics, e.g. xylene, toluene,naptha, alkanols including cyclic alkanols like cydohexanol, aliphaticsincluding hydrocarbons and chlorinated hydrocarbons are suitable. Hexaneis an especially outstanding solvent as it has the needed solvationpower and presents a fine balance between a short drying, or evaporationtime, and a relatively high flash point.

In the preferred mode of practicing this invention roads are repaired,or even constructed, by applying the primer composition to a roadsubstrate, e.g. concrete, asphalt, brick and the like, and after solventevaporation a road repair membrane is positioned in direct contact withthe primer. If, for example, cracks are also being repaired, a suitablerepair binder, e.g. asphalt or ROADBOND™ binder, a product of theassignee of this invention, will be dispensed into the crack and theprimer then applied to the substrate adjacent the filled crack. The roadrepair membrane, or laminant, preferably comprises a fibrousreinforcement material which has been coated, or impregnated, on bothsides, as by dipping, with a substantially non-tacky chemically-modifiedasphalt, the membrane also being provided, as by coating on one sidethereof, with a layer of the adhesive which serves to tenaciouslyenhance the membrane bonding to the primer.

Desirably the membrane will be sufficiently flexible to allow it to beformed into rolls and in order to protect the adhesive layer and preventmembrane adherence in the rolled form prior to the time of use, theadhesive layer will be covered with a suitable removable, orreleaseable, skin as in the form of a tear-away strip. Reference hereinto substantially non-tacky means that at room temperature thechemically-modified asphalt has significantly less tack than theadhesive.

Exemplary fibrous reinforcement materials are various mats includingchopped strand mats, continuous strand mats, swirl mats, woven andnon-woven fabrics, e.g., woven rovings, insect screening, scrim and thelike. Preferably the fibrous materials are glass but they may also beorganic polymeric materials or combinations of glass and organicpolymers. Outstanding results are obtained when the non-tackychemically-modified asphalt is the reaction product of asphalt,non-depolymerized rubber and a polymerizable vinyl aromatic monomer; thelatter may be an admixture of monofunctional and polyfunctional vinylmonomers. Further details may be found in copending applications Ser.No. 045,047 (now U.S. Pat. No. 4,273,685) and Ser. No. 144,711 (now U.S.Pat. No. 4,332,705) both of which are hereby incorporated by reference.Suitably the non-tacky chemically-modified asphalt coating is applied tothe reinforcement material by dipping the latter into a hot melt of theformer. The coated membrane may then be cooled and the adhesive appliedto one side. The releaseable skin is then applied to the adhesive layer.The adhesive may likewise be applied as a hot melt. One suitablereleaseable skin is a polyethylene coated kraft paper which has asilicone overcoat which is available from Daubert Paper Co. as theirproduct 1-60-EKPL-164. The membrane is then preferably rolled uponitself to form a roll for on site use in road repairs by applying it tothe primer.

Having described the basic concepts of the invention, reference is nowmade to the following examples, which are provided by way ofillustration, and not by way of limitation, of the practice of thepresent invention in formulating a primer composition and its use inpromoting a secure bonding relationship between an adhesive coating matand a substrate over which the mat is laid down.

EXAMPLE 1

This example illustrates the preparation of a primer compositionembodying the concepts of this invention.

A primer batch is formulated as follows:

    ______________________________________                                                            Parts by weight                                           ______________________________________                                        Depolymerized natural rubber                                                                        60                                                      (DPR-400)                                                                     Depolymerized natural rubber                                                  (XL-01) (From Hardman Chemicals)                                                                    6                                                       Terpene resin (Piccolyte A-115                                                                      229                                                     resin)                                                                        ______________________________________                                    

The above batch is cooked at 165° F. for 4 hours. Thereafter, thereaction product is blended with hexane to form a primer formulation ofabout 10%-12% by weight of solids, which is then applied to a roadsurface. Thereafter, glass fibers (in the form of a woven roving coatedon both sides by dipping in a chemically-modified asphalt and thencoated on one side with an adhesive formed by the reaction of asphalt,styrene, a rubbery polymer, a depolymerized rubber and a terpene resin)is laid down over the primed surface with the adhesive in direct contactwith the primer. It is found that the adhesion is improved by 15-30% ascompared to the same surface which has not been coated with a primer. Inaddition, adhesion is achieved at temperatures 10° F. to 15° F. lowerthan the temperatures required to secure adhesion to the same surfacewhich had not been coated with a primer

EXAMPLE 2

This example illustrates the preparation of a primer composition of theinvention which has been formulated to include a non-depolymerizedrubber, namely Solprene 1205C, a butadiene-styrene rubber.

A primer batch is formulated as follows:

    ______________________________________                                                          Parts by weight                                             ______________________________________                                        Depolymerized natural rubber                                                                      1                                                         (XL-01)                                                                       Butadiene-styrene rubber                                                                          10                                                        (Solprene 1205C)                                                              Nevpene (9500)      20                                                        Naphtha (55° F.)                                                                           100                                                       ______________________________________                                    

The above formulation was made at room temperature and was allowed tostand for 24 hours. Mixing is used to cause the depolymerized rubber togo into solution.

The resulting primer composition is then applied to a stainless steelsheet at a thickness of 0.006 in., and a glass-reinforced mat of treatedasphalt applied to it. The adhesion between the mat and the stainlesssteel substrate is improved as compared to a stainless steel substratewhich had not been coated with the primer.

It will be understood that various modifications can be made in thedetails of procedure, formulation and use without departing from thespirit of the invention, especially as defined in the following claims.

We claim:
 1. A primer composition for use in improving the bondingrelationship of asphalts to substrates, said composition consistingessentially of the reaction product of (1) 5 to 40% by weight of aliquid tacky depolymerized rubber and (2) 95 to 40% by weight of aterpene resin, wherein said liquid cacky depolymerized rubber is a dienerubber having an average molecular weight below about 110,000.
 2. Acomposition as defined in claim 1 wherein the terpene resin is asynthetic polyterpene derived from a C₅ hydrocarbon resin.
 3. Acomposition as defined in claim 1 wherein the terpene resin is derivedfrom alpha-pinene.
 4. A composition as defined in claim 1 which includesa solvent.
 5. A composition as defined in claim 1 wherein thecomposition also includes a non-depolymerized rubber.
 6. A compositionas defined in claim 1 wherein the composition is formed at a temperaturewithin the range of 50°-300° F.
 7. A composition defined in claim 5which includes a non-depolymerized rubber in an amount ranging from 1 to30% by weight.